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      <td width="885"><font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">The Context Object</font></b></font></td>
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<blockquote>
  <p><a href="class_reference_context.html#introduction">Introduction</a><br>
    <a href="class_reference_context.html#header_synopsis">Header
    'wave/context.hpp' synopsis</a><br>
    <a href="class_reference_context.html#public_typedefs">Public
    Typedefs</a><br>
    <a href="class_reference_context.html#template_parameters">Template
    parameters</a><br>
    <a href="class_reference_context.html#member_functions">Member
    functions</a></p>
</blockquote>
<h2><b><a name="introduction"></a>Introduction</b></h2>
<p>The <tt>boost::wave::context&lt;&gt;</tt> object is the main user visible object of the <tt>Wave</tt> library. It exists to generate the pair of iterators, which while
  dereferenced return the preprocessed tokens. Additionally it is used to
  control other aspects of the preprocessing, such as </p>
<blockquote>
  <p><strong><img id="IMG1" src="theme/bullet.gif" height="13" width="13"></strong>&nbsp;include
    search paths, which define, where to search for files to be included
    with <tt>#include&nbsp;&lt;...&gt;</tt> and <tt>#include&nbsp;"..."</tt> directives<br>
    <strong><img src="theme/bullet.gif" height="13" width="13">&nbsp;</strong>which macros to
    predefine and which of the predefined macros to undefine<br>
    <strong><img src="theme/bullet.gif" height="13" width="13">&nbsp;</strong>several other options as
    for instance to control, whether to enable several extensions to the
    C++ Standard (as for instance variadics and placemarkers) or not.</p>
</blockquote>
<h2><b><a name="header_synopsis"></a>Header <a href="http://svn.boost.org/trac/boost/browser/trunk/boost/wave/cpp_context.hpp">wave/cpp_context.hpp</a> synopsis</b></h2>
<pre><span class="keyword">namespace</span> <span class="identifier">boost</span> {<br><span class="keyword">namespace</span> <span class="identifier">wave</span> { <br> <br> <span class="keyword">   struct</span> this_type {};<br><br>    <span class="keyword">template</span> &lt;<br>        <span class="keyword">typename</span> Iterator, <span class="keyword">typename</span> LexIterator, <br>        <span class="keyword">typename</span> InputPolicy, <span class="keyword">typename</span> ContextPolicy,<br>        <span class="keyword">typename</span> Derived = this_type<br>    &gt; <br> <span class="keyword">   class</span> context <span class="special">:</span> <span class="keyword">public</span> InputPolicy <br>    {<br>        <span class="keyword">typedef</span> &lt;unspecified&gt; token_sequence_type;<br><br>    <span class="keyword">public</span>: <br><br> <span class="keyword">       typedef</span> pp_iterator&lt;context&gt; iterator_type; <br>        <span class="keyword">typedef</span> Token token_type;<br>        <span class="keyword">typedef</span> <span class="keyword">typename</span> token_type::position_type position_type;<br>        <span class="keyword">typedef</span> std::list&lt;token_type&gt; token_sequence_type;<br><br><span class="comment">    // constructor</span><br>        <a href="class_reference_context.html#constructor">context</a>(Iterator<span class="keyword"> const</span> &amp;first_, <br>            Iterator <span class="keyword">const</span> &amp;last_, <br>            <span class="keyword">char const</span> *fname = <span class="string">"&lt;Unknown&gt;"</span>,<br>            ContextPolicy <span class="keyword">const</span>&amp; ctx_policy = ContextPolicy())<br><br>    <span class="comment">// iterator interface</span><br>        iterator_type <a href="class_reference_context.html#iterator_interface_begin">begin</a>() <span class="keyword">const</span>;<br>        iterator_type <a href="class_reference_context.html#iterator_interface_begin">begin</a>(Iterator<span class="keyword"> const</span> &amp;first, <br>            Iterator <span class="keyword">const</span> &amp;last) <span class="keyword">const</span>;<br>        iterator_type <a href="class_reference_context.html#iterator_interface_end">end</a>() <span class="keyword">const</span>;<br><br>    <span class="comment">// maintain include paths</span><br><span class="keyword">        bool</span> <a href="class_reference_context.html#add_include_path">add_include_path</a>(<span class="keyword">char const</span> *path_);<br>        <span class="keyword">bool</span> <a href="class_reference_context.html#add_sysinclude_path">add_sysinclude_path</a>(<span class="keyword">char const</span> *path_);<br>        <span class="keyword">void</span> <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter</a>();<br> <br>        size_t <a href="class_reference_context.html#get_iteration_depth">get_iteration_depth</a>() <span class="keyword">const</span>;<br><br> <span class="comment">   // maintain defined macros</span><br>        <span class="keyword">template</span> &lt;<span class="keyword">typename</span> String&gt;<br><span class="keyword">        bool</span> <a href="class_reference_context.html#add_macro_definition">add_macro_definition</a>(<span class="keyword">String</span> macrostring, <br>        <span class="keyword">    bool</span> is_predefined = <span class="keyword">false</span>);<br>        <span class="keyword">template</span> &lt;<span class="keyword">typename</span> String&gt;<br><span class="keyword"></span>        <span class="keyword">bool</span> add_macro_definition(StringT <span class="keyword">const</span> &amp;name, <br>            position_type <span class="keyword">const</span>&amp; pos, <span class="keyword">bool</span> has_params, <br>            std::vector&lt;token_type&gt; &amp;parameters, <br>            token_sequence_type &amp;definition, <br>            <span class="keyword">bool</span> is_predefined = <span class="keyword">false</span>)<br><br>        <span class="keyword">template</span> &lt;<span class="keyword">typename</span> String&gt;<br>        <span class="keyword">bool</span> <a href="class_reference_context.html#is_defined_macro">is_defined_macro</a>(<span class="keyword">String const</span> &amp;name) <span class="keyword">const</span>;<br>        <span class="keyword">template</span> &lt;<span class="keyword">typename</span> String&gt;<br>        <span class="keyword">bool</span> <a href="class_reference_context.html#remove_macro_definition">remove_macro_definition</a>(String<span class="keyword"> const</span> &amp;name, <br>        <span class="keyword">    bool</span> even_predefined = <span class="keyword">false</span>);<br>        <span class="keyword">void</span> <a href="class_reference_context.html#reset_macro_definitions">reset_macro_definitions</a>();<br>        <span class="keyword">template</span> &lt;<span class="keyword">typename</span> String&gt;<br> <span class="keyword">       bool</span> <a href="class_reference_context.html#get_macro_definition">get_macro_definition</a>(<br> <span class="keyword">           </span>String<span class="keyword"> const</span> &amp;name, <span class="keyword">bool</span> &amp;is_function_style, <span class="keyword"><br>            bool</span> &amp;is_predefined, position_type &amp;pos, <br>            std::vector&lt;token_type&gt; &amp;parameters, <br>            token_sequence_type &amp;definition) <span class="keyword">const</span>; <br><br>        <span class="keyword">typedef</span> &lt;unspecified&gt; macromap_type;<br>        <span class="keyword">typedef</span> typename macromap_type::name_iterator name_iterator;<br>        <span class="keyword">typedef</span> typename macromap_type::const_name_iterator const_name_iterator;<br><br>        name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_begin</a>();<br>        name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_end</a>();<br>        const_name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_begin</a>() <span class="keyword">const</span>;<br>        const_name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_end</a>() <span class="keyword">const</span>;<br><br>    <span class="comment">// other options</span><br><span class="keyword">        void</span> <a href="class_reference_context.html#language_support">set_language</a>(language_support enable);<br>        language_support <a href="class_reference_context.html#language_support">get_language</a>() <span class="keyword">const</span>;<br><br><span class="keyword">        void</span> <a href="class_reference_context.html#set_max_include_nesting_depth">set_max_include_nesting_depth</a>(std::size_t new_depth);<br>        size_t <a href="class_reference_context.html#set_max_include_nesting_depth">get_max_include_nesting_depth</a>() <span class="keyword">const</span>;<br><br><span class="comment">    // get the Wave version information </span><br><span class="keyword">        static std::string</span> <a href="class_reference_context.html#get_version">get_version</a>();<br>        <span class="keyword">static std::string</span> <a href="class_reference_context.html#get_version">get_version_string</a>();<br>    };<br><br>} <span class="comment">// namespace wave</span><br>} <span class="comment">// namespace boost</span></pre>
<h2><b><a name="template_parameters"></a>Template
  parameters</b></h2>
<p>The <tt>boost::wave::context</tt> object has
  three template parameters to specify the concrete behaviour of its
  operation. The following table describes these with more detail.</p>
<table align="center" border="0" width="90%">
  <tbody>
    <tr>
      <td colspan="2" class="table_title"><b>Template
        parameters required for the <tt>boost::wave::context</tt> class </b></td>
    </tr>
    <tr>
      <td class="table_cells" width="32%"><code>Iterator</code></td>
      <td class="table_cells" width="68%"><p>The type of the underlying iterator, through which the
          input stream is accessed. <br>
          This should be at least an <tt>forward_iterator</tt> type
          iterator.</p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>LexIterator</code></td>
      <td class="table_cells"><p>The type of the lexer type to be used by the <tt>Wave</tt> library to identify tokens in the input stream.</p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>InputPolicy</code></td>
      <td class="table_cells"><p>The type of the input policy class, which allows to
          customize the behaviour of the Wave library and the type of the
          iterators to use, when it comes to including and opening an included
          file.</p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>ContextPolicy</code></td>
      <td class="table_cells"><p>The type of the context policy class, which allows to
          customize different aspects of the behaviour of the preprocessing. The
          requirements of this policy and the available customization points
          provided by this policy are described <a href="class_reference_ctxpolicy.html">here</a>.&nbsp;&nbsp;
          &nbsp;</p></td>
    </tr>
    <tr class="table_cells">
      <td class="table_cells"><code>Derived</code></td>
      <td><p>The type of the type being derived from the context type (if
          any). This template parameter is optional and defaults to 'this_type',
          which means that the context&nbsp;type will be used assuming no derived type exists. <br>
        </p></td>
    </tr>
  </tbody>
</table>
<p>For further information about the lexer type to use, please
  refer to the <a href="class_reference_lexer.html">The
  Lexer Interface </a>.</p>
<p>If the template parameter <tt>InputPolicy</tt> is
  omitted, the template <tt>boost::wave::iteration_context_policies::load_file_to_string</tt> is used. For further information about the input policy, please refer
  to the topic <a href="class_reference_inptpolcy.html">The
  Input Policy</a>.</p>
<p>If the template parameter ContextPolicy is omitted, the <tt>boost::wave::context_policies::eat_whitespace</tt> policy type is used, implementing certain basic preprocessing hooks
  needed for normal (default) execution. For further information about
  the context policy, please refer to the topic <a href="class_reference_ctxpolicy.html">The Context Policy</a>. </p>
<h2><a name="public_typedefs"></a>Public
  Typedefs</h2>
<p>The <tt>boost::wave::context</tt> template
  defines the following public typedefs, which may be useful while using
  this class:</p>
<table align="center" border="0" width="90%">
  <tbody>
    <tr>
      <td colspan="2" class="table_title"><b>Public
        typedefs defined by the <tt>boost::wave::context</tt> class </b></td>
    </tr>
    <tr>
      <td class="table_cells"><code>iterator_type</code></td>
      <td class="table_cells"><p>The <tt>Iterator</tt> template parameter
          provided, while the <tt>context</tt> class was
          instantiated. </p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>lex_type</code></td>
      <td class="table_cells"><p>The <tt>LexIterator</tt> template parameter
          provided, while the <tt>context</tt> class was
          instantiated. </p></td>
    </tr>
    <tr>
      <td class="table_cells" width="32%"><code>token_type</code></td>
      <td class="table_cells" width="68%"><p>The token type, which is returned by the <tt>context</tt> generated iterators. This type is taken from the <tt>LexIterator</tt> template parameter provided, whicle the <tt>context</tt> class was instantiated.</p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>input_policy_type</code></td>
      <td class="table_cells"><p>The <tt>InputPolicy</tt> template parameter
          provided, while the <tt>context</tt> class was
          instantiated. </p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>context_policy_type</code></td>
      <td class="table_cells"><p>The <tt>ContextPolicy</tt> template
          parameter provided, while the <tt>context</tt> class was
          instantiated. </p></td>
    </tr>
    <tr>
      <td class="table_cells"><code>position_type</code></td>
      <td class="table_cells"><p>The type of the position information contained in every
          returned token, which describes the point, at which the given token was
          recognised. </p></td>
    </tr>
  </tbody>
</table>
<h2><b><a name="member_functions"></a>Member
  functions</b></h2>
<p><b><a name="constructor" id="constructor"></a>Constructor</b></p>
<pre>    context(Iterator <span class="keyword">const</span> &amp;first, <br>        Iterator <span class="keyword">const</span> &amp;last, <span class="keyword">char</span> <span class="keyword">const</span> *filename, <br>        ContextPolicy <span class="keyword">const</span>&amp; ctx_policy);</pre>
<p>Constructs a context object on top of the input stream given
  by the pair of auxilliary iterators <tt>[first,&nbsp;last)</tt>.
  The iterators should be at least <tt>forward_iterator</tt> type iterators. The filename parameter is to be supplied for
  informational purposes only. This string is used for indicating the
  token positions inside the input stream, it is not validated against
  the file system. If the filename parameter is not given it defaults to <span class="copyright">"&lt;Unknown&gt;"</span>. If
  the ctx_policy parameter isn't supplied it defaults to a default
  constructed <tt>ContextPolicy</tt> object. </p>
<p>Additionally the macro symbol table is filled with the
  predefined macros and the current reference directory is set to the
  path of the given filename. If this filename does not reference valid
  file system item, the current reference directory is set to the current
  system directory. (The current reference directory is the file system
  path, which is used as the target directory during the processing of <tt>#include&nbsp;"..."</tt> directives).</p>
<h3>Iterator interface</h3>
<p>The pair of iterators returned by the <tt>context::begin</tt> and <tt>context::end</tt> functions is the main interface
  for accessing the preprocessed tokens from the preprocessor engine.
  While iterating over the given iterator range <tt>[begin,&nbsp;end)</tt> there are returned the preprocessed C++ tokens, which are generated on
  the fly from the underlying input stream. The returned iterators are
  conceptually of <tt>forward_iterator</tt> type.</p>
<p><b><a name="iterator_interface_begin"></a></b><b>begin</b></p>
<pre>    iterator_type begin();<br>    iterator_type begin(Iterator <span class="keyword">const</span> &amp;first,<br>         Iterator <span class="keyword">const</span> &amp;last, <span class="keyword"></span>);</pre>
<blockquote>
  <p>Initializes and returns the starting iterator for the
    preprocessed token stream. The iterator pair given by the parameters&nbsp; <tt>[first,&nbsp;last)</tt> specifies the input sequence to preprocess. The first version of this
    function uses the input stream as specified by the constructor.&nbsp;</p>
</blockquote>
<p><b><a name="iterator_interface_end" id="iterator_interface_end"></a></b><b>end</b></p>
<pre>    iterator_type end() <span class="keyword">const</span>;</pre>
<blockquote>
  <p>Initializes and returns the end of stream iterator to
    compare with for detecting the end of the preprocessed token stream.</p>
</blockquote>
<h3>Maintain include paths</h3>
<p>The <tt>Wave</tt> library maintains two separate
  search paths for include files. A search path for user include files
  and a search path for system include files. Any directories specified
  with the <a href="#add_include_path">add_include_path()</a> function before the function <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter()</a> is called are searched only for the case of <tt>#include&nbsp;"..."</tt> directives, they are not searched for <tt>#include&nbsp;&lt;file&gt;</tt> directives. I.e. these directories are added to the user include search
  path. </p>
<p>If additional directories are specified with the <a href="#add_include_path">add_include_path()</a> function after a call to the function <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter()</a>,
  these directories are searched for all <tt>#include</tt> directives. I.e. these directories are added to the system include
  search path.</p>
<p>In addition, a call to the function <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter()</a> inhibits the use of the current reference directory as the first search
  directory for <tt>#include&nbsp;"..."</tt> directives.
  Therefore, the current reference directory is searched only, if it is
  requested explicitly with a call to the function <a href="#add_include_path">add_include_path(".")</a>. </p>
<p>Callig both functions, the <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter()</a> and <a href="#add_include_path">add_include_path(".")</a> allows you to control precisely, which directories are searched before
  the current one and which are searched after.</p>
<p>These functions are modelled after the command line behaviour
  implemented by the popular gcc compiler.<br>
</p>
<p><a name="add_include_path"></a><b>add_include_path</b></p>
<pre> <span class="keyword">   bool</span> add_include_path(<span class="keyword">char const</span> *path);<br>
</pre>
<blockquote>
  <p>Adds the given file system path to the user include search
    paths. After a call to the <a href="class_reference_context.html#set_sysinclude_delimiter">set_sysinclude_delimiter()</a> this function adds the given file system path to the system include
    search paths. Note though, that the given path is validated against the
    file system. </p>
  <p>If the given path string does not form a name of a valid
    file system directory item, the function returns <tt>false</tt>.
    If the given path was successfully added to the include search paths in
    question, the function returns <tt>true</tt>.</p>
</blockquote>
<p><a name="add_sysinclude_path"></a><b>add_sysinclude_path</b></p>
<pre>    <span class="keyword">bool</span> add_sysinclude_path(<span class="keyword">char const</span> *path);</pre>
<blockquote>
  <p>Adds the given file system path to the system include search
    paths. This function operates on the system include search path
    regardless of the mode of operation of the <a href="#add_include_path">add_include_path()</a>. Note
    though, that the given path is validated against the file system.</p>
  <p>If the given path string does not form a name of a valid
    file system directory item, the function returns <tt>false</tt>.
    If the given path was successfully added to the system include search
    paths, the function returns <tt>true</tt>.</p>
</blockquote>
<p><a name="set_sysinclude_delimiter"></a><b>set_sysinclude_delimiter</b></p>
<pre> <span class="keyword">   void</span> set_sysinclude_delimiter();</pre>
<blockquote>
  <p>Switches the mode, how the <a href="#add_include_path">add_include_path()</a> function operates. By default the given file system path is added to
    the user include search paths. After calling this function a subsequent
    call to the <a href="#add_include_path">add_include_path()</a> adds the given file system path to the system include search paths.
    Additionally it inhibits the the use of the current reference directory
    as the first search directory for <tt>#include&nbsp;"..."</tt> directives.</p>
</blockquote>
<p><a name="get_iteration_depth"></a><b>get_iteration_depth</b></p>
<pre>    size_t get_iteration_depth() <span class="keyword">const</span>;</pre>
<blockquote>
  <p>Returns the actual include iteration depth, i.e. the current
    number of include levels to be popped from the include iteration
    context, before the main (topmost) iteration context is reached.</p>
</blockquote>
<h3>Maintain defined macros</h3>
<p><a name="add_macro_definition"></a><b>add_macro_definition</b></p>
<pre><span class="keyword">    bool</span> add_macro_definition(<br> <span class="keyword">       std::string</span> macrostring, <span class="keyword">bool</span> is_predefined); <br>
</pre>
<blockquote>
  <p>Adds a new macro definition to the macro symbol table. The
    parameter <tt>macrostring</tt> should contain the macro to
    define in the command line format, i.e. something like <tt>MACRO(x)=definition</tt>.
    The following table describes this format in more detail. The parameter <tt>is_predefined</tt> should be true while defining
    predefined macros, i.e. macros, which are not undefinable with an <tt>#undef</tt> directive from inside the preprocessed input stream. If this parameter
    is not given, it defaults to <tt>false</tt>.</p>
  <table align="center" border="0" width="90%">
    <tbody>
      <tr>
        <td colspan="2" class="table_title"><b>Summary
          of possible formats for defining macros </b></td>
      </tr>
      <tr>
        <td class="table_cells" width="32%"><code>MACRO</code></td>
        <td class="table_cells" width="68%"><code>define <tt>MACRO</tt> as 1</code></td>
      </tr>
      <tr>
        <td class="table_cells"><code>MACRO=</code></td>
        <td class="table_cells"><code>define <tt>MACRO</tt> as nothing (empty)</code></td>
      </tr>
      <tr>
        <td class="table_cells"><code>MACRO=definition</code></td>
        <td class="table_cells"><code>define <tt>MACRO</tt> as <tt>definition</tt></code></td>
      </tr>
      <tr>
        <td class="table_cells" width="32%"><code>MACRO(x)</code></td>
        <td class="table_cells" width="68%"><code>define <tt>MACRO(x)</tt> as 1</code></td>
      </tr>
      <tr>
        <td class="table_cells"><code>MACRO(x)=</code></td>
        <td class="table_cells"><code>define <tt>MACRO(x)</tt> as nothing (empty)</code></td>
      </tr>
      <tr>
        <td class="table_cells"><code>MACRO(x)=definition</code></td>
        <td class="table_cells"><code>define <tt>MACRO(x)</tt> as <tt>definition</tt></code></td>
      </tr>
    </tbody>
  </table>
  <p>The function returns <tt>false</tt>, if the
    macro to define already was defined and the new definition is
    equivalent to the existing one, it returns true, if the new macro was
    successfully added to the macro symbol table.</p>
  <p>If the given macro definition resembles a redefinition and
    the new macro is not identical to the already defined macro (in the
    sense defined by the C++ Standard), the function throws a corresponding <tt>preprocess_exception</tt>.</p>
</blockquote>
<p><a name="is_defined_macro"></a><b>is_defined_macro</b></p>
<pre> <span class="keyword">   template</span> &lt;<span class="keyword">typename</span> String&gt;<br>    <span class="keyword">bool</span> is_defined_macro(String <span class="keyword">const</span> &amp;name) <span class="keyword">const</span>; </pre>
<blockquote>
  <p>Returns, if a macro with the given <tt>name</tt> is defined, i.e. if it is contained in the macro symbol table.</p>
</blockquote>
<p><strong><a name="get_macro_definition"></a>get_macro_definition</strong></p>
<pre> <span class="keyword">   template</span> &lt;<span class="keyword">typename</span> String&gt;<br>    <span class="keyword">bool</span> get_macro_definition(<br> <span class="keyword">       </span>String<span class="keyword"> const</span> &amp;name, <span class="keyword">bool</span> &amp;is_function_style, <span class="keyword"><br>        bool</span> &amp;is_predefined, position_type &amp;pos, <br>        std::vector&lt;token_type&gt; &amp;parameters, <br>        token_sequence_type &amp;definition) <span class="keyword">const</span>; </pre>
<blockquote>
  <p>Allows to retrieve all information known with regard to a
    macro definition. The parameter <tt>name</tt> specifies
    the name of the macro the information should be returned for. The
    parameters <tt>is_function_style</tt> and <tt>is_predefined</tt> return, whether the macro has been defined as a function style macro or
    as a predefined macro resp. The parameter <tt>pos</tt> will contain the position the macro was defined at. The parameter <tt>parameters</tt> will contain the names of the parameters the macro was defined with and
    the parameter <tt>definition</tt> will contain the token
    sequence for the definition (macro body).</p>
  <p>The function returns <tt>true</tt> is the macro
    was defined and the requested information has been successfully
    retrieved, <tt>false</tt> otherwise.</p>
</blockquote>
<p><a name="remove_macro_definition"></a><b>remove_macro_definition</b></p>
<pre><span class="keyword"> </span> <span class="keyword">  template</span> &lt;<span class="keyword">typename</span> String&gt;<br><span class="keyword">    bool</span> remove_macro_definition(<br>        String<span class="keyword"> const</span> &amp;name, <span class="keyword">bool</span> even_predefined); </pre>
<blockquote>
  <p>Removes the definition of the macro with the given <tt>name</tt> from the macro symbol table. This operation is equivalent to an <tt>#undef</tt> directive with this <tt>name</tt> executed from within the
    input stream. If the parameter <tt>even_predefined</tt> is <tt>true</tt>, then the macro is removed from the macro
    symbol table even, if it is defined as a predefined macro. </p>
  <p>Note though, that the following macros are <b>not</b> undefinable in any case: <tt>__FILE__</tt>, <tt>__LINE__</tt>, <tt>__DATE__</tt>, <tt>__TIME__</tt>, <tt>__cplusplus</tt>, <tt>__STDC__</tt>. If the parameter <tt>even_predefined</tt> is not given, it defaults to <tt>false</tt>.</p>
  <p>The function returns <tt>false</tt>, if the
    macro to undefine was not defined and returns <tt>true</tt> otherwise.</p>
  <p>If the macro to remove may not be undefined (it is a
    predefined macro and the parameter <tt>even_predefined</tt> is set to <tt>false</tt> or it is one of the mentioned not
    undefinable macros above) the function throws a <tt>preprocess_exception</tt>.</p>
</blockquote>
<p><a name="reset_macro_definitions"></a><b>reset_macro_definitions</b></p>
<pre><span class="keyword">    void</span> reset_macro_definitions(); </pre>
<blockquote>
  <p>Resets the macro symbol table to it's initial state, i.e.
    undefines all user defined macros and inserts the internal predefined
    macros as described <a href="predefined_macros.html">here</a>.</p>
</blockquote>
<p><a name="macro_names_iterators"></a><b>macro_names_begin,
  macro_names_end </b></p>
<pre>    name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_begin</a>();<br>    name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_end</a>();<br>    const_name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_begin</a>() <span class="keyword">const</span>;<br>    const_name_iterator <a href="class_reference_context.html#macro_names_iterators">macro_names_end</a>() <span class="keyword">const</span>;<br>
</pre>
<blockquote>
  <p>The <tt>macro_names_begin</tt> and <tt>macro_names_end</tt> functions return iterators allowing to iterate on the names of all
    defined macros.</p>
</blockquote>
<h3><a name="get_version"></a>Get Version
  information</h3>
<p><b>get_version</b></p>
<pre><span class="keyword"> </span><span class="keyword">   static std::string</span> get_version(); </pre>
<blockquote>
  <p>Returns a string containing the current Wave version
    formatted as <span class="string">0xvvrsbbbb</span> (this is a string representation of the equivalent hexadecimal number),
    where <span class="literal">'vv'</span> is the
    version number, <span class="literal">'r'</span> the release number, <span class="literal">'s'</span> the subrelease number and <span class="literal">'bbbb'</span> the build number. A possible return value looks like <span class="literal">0x00910454</span>. The returned value
    is the same as is inserted in the preprocessed token stream, when the
    predefined macro <tt>__WAVE_VERSION__</tt> is expanded.</p>
</blockquote>
<p><b>get_version_str</b></p>
<pre><span class="keyword"> </span><span class="keyword">   static std::string</span> get_version_str(); </pre>
<blockquote>
  <p>Returns a string containing the current Wave version
    formatted as <span class="string">"v.rr.ss.bbbb"</span>,
    where <span class="literal">'v'</span> is the
    version number, <span class="literal">'rr'</span> the release number, <span class="literal">'ss'</span> the subrelease number and <span class="literal">'bbbb'</span> the build number. A possible return value looks like <span class="literal">"0.9.1.454"</span>. The returned value
    is the same as it will be inserted in the preprocessed token stream,
    when the predefined macro <tt>__WAVE_VERSION_STR__</tt> is
    expanded.</p>
</blockquote>
<h3>Control extended options</h3>
<p><a name="language_support"></a>set_language<br>
  get_language</p>
<pre><span class="keyword">    void</span> set_language(<span class="keyword">language_support</span> language, <br>        <span class="keyword">bool</span> reset_macros = <span class="keyword">true</span>);<br>    <span class="keyword">language_support</span> get_language() <span class="keyword">const</span>;</pre>
<blockquote>
  <p>This functions allows to specify the language mode, in which
    the <tt>Wave</tt> library should work. The possible
    language modes are defined by the enumerated type <tt>language_support</tt>:</p>
  <pre>    <span class="keyword">enum</span> language_support {<br>    <span class="comment">// support flags for C++98</span><br>        support_normal = 0x01,<br>        support_cpp = support_normal,<br><span class="comment"><br>    // support flags for C99</span><br>        support_option_long_long = 0x02,<br>        support_option_variadics = 0x04,<br>        support_c99 = support_option_variadics | support_option_long_long | 0x08,<br><span class="comment"><br>    // support flags for C++11</span><br>        support_option_no_newline_at_end_of_file = 0x20,<br>        support_cpp0x = support_option_variadics | support_option_long_long |<br>            support_option_no_newline_at_end_of_file | 0x10,<br>        support_cpp11 = support_cpp0x,    <br><br><span class="comment">    //  support flags for C++17</span><br>        support_option_has_include = 0x10000,<br>        support_cpp1z = support_option_variadics | support_option_long_long |<br>            support_option_no_newline_at_end_of_file | support_option_has_include | 0x20000,<br>        support_cpp17 = support_cpp1z<br><br><span class="comment">    //  support flags for C++20</span><br>        support_option_va_opt = 0x40000,<br>        support_cpp2a = support_option_variadics | support_option_long_long |<br>            support_option_no_newline_at_end_of_file | support_option_has_include |<br>            support_option_va_opt | 0x80000,<br>        support_cpp20 = support_cpp2a,<br><span class="comment"><br>    // the mask for the main language settings</span><br>        support_option_mask = 0xFFC0,<br><br><span class="comment">    // additional fine tuning of the general behavior</span><br>        support_option_emit_contline = 0x0040,<br>        support_option_insert_whitespace = 0x0080,<br>        support_option_preserve_comments = 0x0100,<br>        support_option_no_character_validation = 0x0200,<br>        support_option_convert_trigraphs = 0x0400,<br>        support_option_single_line = 0x0800,<br>        support_option_prefer_pp_numbers = 0x1000,<br>        support_option_emit_line_directives = 0x2000,<br>        support_option_include_guard_detection = 0x4000,<br>        support_option_emit_pragma_directives = 0x8000<br>    };</pre>
  <p>When used with <tt>support_option_variadics</tt> the support for variadics, placemarkers and the <tt>operator&nbsp;_Pragma()</tt> is enabled in normal C++ mode. When used with the <tt>support_option_long_long</tt> the support for long long suffixes is enabled in C++ mode. </p>
  <p>The <tt>support_c99</tt> switches on the C99
    language support, which enables variadics, placemarkers, the <tt>operator&nbsp;_Pragma</tt> and long long suffixes by default. Additionally it disables the C++
    specific tokens such as <tt>'-&gt;*'</tt>, <tt>'.*'</tt>, <tt>'::'</tt> etc. </p>
  <p>The <tt>support_option_...</tt> values are to
    be used in conjunction with the main language settings (<tt>support_normal</tt> and <tt>support_c99</tt>) . </p>
  <ul>
    <li>If the <tt>support_option_insert_whitespace</tt> flag is set,&nbsp;the <tt>Wave</tt> library &nbsp;inserts
      additional whitespace between tokens where the concatenated string
      representation of the two tokens would form another valid C++ token.
      This is very important to avoid mis-interpretations of the generated
      output if it is going to be processed by a C++ compiler afterwards.
      &nbsp; </li>
    <li>If the <tt>support_option_preserve_comments</tt> flag is set, the <tt>Wave</tt> library preserves almost
      all comments in the source code. The only comments not preserved are
      those contained inside macro definitions. If this flag is not set all
      comments are replaced by a single space. </li>
    <li>If the <tt>support_option_no_character_validation</tt> flag is set , the <tt>Wave</tt> library does not validate
      universal character literals (given in the form of <tt>'u1234'</tt> or <tt>'U12345678'</tt>) to be in the allowed value range.
      This flag is merely used for internal purposes by the testing framework
      and will be rarely used by a user of the library.</li>
    <li>If the <tt>support_option_convert_trigraphs</tt> flag is set, the <tt>Wave</tt> library replaces all
      occurrences of trigraph characters with their non-trigraph character
      sequence (i.e. <tt>'??='</tt> is replaced by <tt>'#'</tt> etc.) . By default no replacement is performed. </li>
    <li>If the <tt>support_option_single_line</tt> flag is set, the <tt>Wave</tt> library runs in <em>single line</em> mode and, among other things, will not report an
      error if the last line of the processed input is not terminated by a
      new line. This flag is mainly used for internal purposes by the testing
      framework and will be rarely used by a user of the library. To disable newline at end of file checking, use <tt>support_option_no_newline_at_end_of_file</tt> (the default for C++11 and later).</li>
    <li>If the <tt>support_option_prefer_pp_numbers</tt> flag is set, the <tt>Wave</tt> library is instructed to
      correctly identify pp-number's in the input stream. These get
      recognized into 'normal' number tokens before they get returned to the
      calling application. The flag is set by default and is used merely for
      internal purposes and will be rarely reset by a user of the library. </li>
    <li>If the <span class="keyword">support_option_emit_line_directives</span> flag is set, the <tt>Wave</tt> library will emit <span class="preprocessor">#line</span> directives in the
      generated token stream, if appropriate. This flag is set by default, to
      prevent the library from generating <span class="preprocessor">#line</span> directives it must be reset explicitly. </li>
    <li>If the <span class="keyword">support_option_include_guard_detection</span> flag is set, the <tt>Wave</tt> library will try to
      automatically identify include guards during the processing of a
      included file. Files which contained include guards are handled as if
      they contained a #pragma once, i.e. these files wonn#t be opened twice,
      even if specified in a second <span class="preprocessor">#include</span> statement. </li>
  </ul>
  <blockquote>
    <p>During this process the library will recognize two forms
      of include guards:</p>
    <pre> <span class="preprocessor">#ifndef</span> INCLUDE_GUARD_MACRO<br> <span class="preprocessor">#define</span> INCLUDE_GUARD_MACRO<br> ...<br> <span class="preprocessor">#endif</span><br>or<br><span class="preprocessor"> #if</span> !defined(INCLUDE_GUARD_MACRO)<br> <span class="preprocessor">#define</span> INCLUDE_GUARD_MACRO<br> ...<br> <span class="preprocessor">#endif</span></pre>
    <p> Note, that the parenthesis in the second form are
      optional (i.e. <tt>!defined INCLUDE_GUARD_MACRO</tt> will
      work as well). The code allows for any whitespace, newline and single
      '#' tokens before the <span class="preprocessor">#if</span>/<span class="preprocessor">#ifndef</span> and after the
      final <span class="preprocessor">#endif</span> for
      the include guard to be recognized.</p>
    <p>This flag is on by default, so if you do not want the
      library to automatically recognize include guards you will need to reset
      this explicitly. </p>
  </blockquote>
  <ul>
    <li>If the <tt>support_option_emit_pragma_directives</tt> flag is set, the <tt>Wave</tt> library will emit all
      unknown <span class="preprocessor">#pragma</span> directives to the output. This support option will be recognized only if
      the <tt>BOOST_WAVE_EMIT_PRAGMA_DIRECTIVES</tt> is defined
      during compilation to a value not equal to zero (see <a href="compiletime_config.html">here</a> for more
      information). </li>
    <li>If the <tt>support_option_emit_contlines</tt> flag is set, the <tt>Wave</tt> library will emit all backslash newline sequences encountered in the input. It will generate a <tt>T_CONTLINE</tt> token for each of those character sequences. Please note that this option is supported by the custom SLex lexer module only. See the cpp_tokens example for a working example.</li>
  </ul>
  <p><strong> </strong>If the parameter <tt>reset_macros</tt> is true the <tt>set_language</tt> function internally
    resets the list of defined macros, so please be careful not to call it
    after you have defined your own macros already. </p>
</blockquote>
<p><a name="set_max_include_nesting_depth" id="set_max_include_nesting_depth"></a>set_max_include_nesting_depth<br>
  get_max_include_nesting_depth</p>
<pre><span class="keyword">    void</span> set_max_include_nesting_depth(size_t new_depth); <br>    size_t get_max_include_nesting_depth() <span class="keyword">const</span>;</pre>
<blockquote>
  <p>This functions allow to set or to get the maximal possible
    include file nesting depth supported by the <tt>Wave</tt> library. The initial value for this is determined by the preprocessing
    constant <tt>WAVE_MAX_INCLUDE_LEVEL_DEPTH</tt> (see <a href="compiletime_config.html">here</a>).</p>
</blockquote>
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